1. Field of the Invention
The present invention relates to a method and an apparatus for jetting ink droplets through a small discharge port onto a recording member to record data.
2. Description of the Prior Art
The ink jet recording method has advantages that noise generation can be prevented at the time of the recording operation and that a high-resolution recorded image can be obtained at high speed due to its highly-integrated head. The foregoing ink jet recording method has conventionally employed ink of a type prepared by dissolving a water-soluble dye selected from a variety of available dyes in water or in a mixture solution of water and a water-soluble organic solvent. However, the recorded image formed by using ink of the foregoing type frequently raises a problem of unsatisfactory fastness such as light resistance and water resistance. In particular, black images usually used in public documents and so forth must exhibit excellent fastness, and accordingly, further improved fast inks have been desired.
Accordingly a variety of investigations have been made for the purpose of preparing ink of a type in which pigment-dispersed fluid, in which a pigment is dispersed in a polymeric dispersant, is dissolved in water or in a mixture solution of water and a water-soluble solvent because excellent water resistance and light resistance can be obtained in comparison to ink of a type containing a water-soluble dye.
In Japanese Patent Laid-Open Nos. 56-147859 and 56-147860 and so forth, pigment ink prepared by using a specific water-soluble organic solvent and a polymer dispersant has been suggested. Further, ink of a type using both a pigment and a water-soluble dye has been suggested in Japanese Patent Laid-Open No. 4-57859 and 4-57860 and so forth.
However, the foregoing conventional pigment ink raises a problem in that the quality of the formed image deteriorates and the density of the same decreases depending upon the type of paper used, for example, where data is recorded on a common paper sheet (usual paper for office use such as copying paper or bond paper). Since the common paper sheet has a surface condition that is not constant, as contrasted with special paper for the ink jet printing operation, the quality of the recorded image varies due to the difference in the ink absorption characteristics of the paper surface due to bleeding. When the density of an image which determines the quality of the recorded article is considered, the surface condition of a recording member, on which data is recorded by using ink containing a water-soluble dye, does not considerably affect the density of a formed image. The reason for this is that the dye adheres to the fiber of the recording member and the dye can easily be left on the surface thereof. On the other hand, pigment ink forms an image by leaving and fixing the pigment on the surface of the recording member. Therefore, the surface condition of the recording member considerably affects the density of a formed image. What is worse, the recorded article obtained by using the pigment exhibits unsatisfactory abrasion resistance, for example, resistance against rubbing with the finger because the pigment is left on the surface of the recording member. In contrast to ink for writing materials, ink for use in ink jet recording operations must simultaneously satisfy many technical requirements, such as discharge stability, long-term dispersion stability (storage stability) and clogging prevention at the fine leading portion of the nozzle and the like. Therefore, all of the foregoing problems cannot be overcome by simply improving the composition of the ink.